Technology
Engineers at the University of Wisconsin-Madison in the United States have used supersonic cold spraying technology to produce a new "workhorse" material for nuclear fusion that can withstand the harsh conditions inside fusion reactors. This development, recently published in the journal Physics Writing, contributes to the achievement of more efficient compact fusion reactors.
Fusion scientists are desperately looking for an economical way to make components that can face high-temperature plasma in fusion reactors.
In a fusion device, plasma (a type of ionized hydrogen) is heated to extremely high temperatures, and the nuclei in the plasma collide with each other and fuse. This fusion process produces energy. However, some hydrogen ions may be neutralized and escape from the plasma. These hydrogen-neutral particles cause power loss in the plasma, making it challenging to maintain high-temperature plasma and operate effective small fusion reactors. This study is the first to demonstrate the benefits of using cold spray technology for fusion applications.
Tantalum is a metal that can withstand high temperatures and excels at capturing hydrogen. The researchers used a cold spray process to deposit a layer of tantalum on the stainless steel. During the spraying process, particles of the coating material are sprayed onto the surface of the stainless steel at supersonic speeds. On impact, the particles flatten like pancakes, covering the entire surface while retaining the nanoscale boundaries between the coated particles. The researchers found that these tiny boundaries help swallow hydrogen particles.
The researchers tested the tantalum coating under the extreme conditions associated with fusion reactors and found that it performed very well. Experiments have also found that when the material is heated to higher temperatures, the tantalum coating is able to spit out trapped hydrogen particles without changing itself. This process essentially regenerates the material so that it can be reused.
The cold spray method not only improves tantalum's ability to capture hydrogen ions, but also allows reactor components to be repaired in the field.
The researchers have created a refractory metal composite material with good hydrogen handling, as well as corrosion resistance and elasticity, which is a breakthrough in the design of plasma devices and fusion energy systems.